Michael Schumacher said a brake issue curtailed his second practice session at the Singapore Grand Prix but he does not think it will be an issue over the rest of the weekend.

Schumacher set the 11th fastest time, 1.923 seconds off the pace, but cut his final session seven minutes short.

"I had a brake issue that's why I stopped," he explained. "We have an issue now and it's certainly something you need to be prepared for."

Mercedes is running a large upgrade package this weekend but Schumacher said it was too early to know whether the team had closed in on its rivals.

"The car feels okay, but I find it difficult to build up a picture of what is happening compared to the competitors. We need more time to analyse that and see who's going to be where, what fuel they are on and where we are. The tyres are very difficult to manage on this track, but it's the same for everybody."

Team principal Ross Brawn agreed that getting the tyres to work would be Mercedes biggest challenge over the rest of the weekend.

"Today was our first outing with our new bodywork and exhaust package at a race weekend, and everything ran reliably. It's clear that getting the tyres to work at their best in the hot and humid conditions is going to be a real challenge for everyone this weekend. We need to make some progress in that area as consistency and degradation of the tyres will be key to having a good race, so that will be a strong focus for what we do overnight.

"We had a slight brake issue with Michael's car at the end of the second session which is why we stopped a little early, otherwise the cars ran well, and we have a lot of good information to look through this evening."